Electric propulsion railway signaling system



W. H. REICHARD ELECTRIC PROPULSION RAILWAY SIGNALING SYSTEM Filed May 25, 1935 Patented Mar. 24, 1936 UNITED STATES PATENT OFFICE ELECTRIC PROPULSION RAILWAY SIGNALING SYSTEM Wade H. Reic'hard, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

This invention relates to railway systems of the electric propulsion type, and more particularly to the construction and bonding of the return connections.

It is generally understood that railways of the electric propulsion type employ a rail or both rails as a return conductor. In the event that the track rails are also used for railway signaling purposes, the track rails are preferably divided into blocks by insulating joints, provision being made for allowing the return current to flow from block to block around the insulating joints and at the same time isolate these blocks from each other insofar as the flow of track circuit current is concerned. This has usually been accomplished by placing aninductance of high value, but of low resistance, across each end of each block and by then connecting the mid-Points of adjacent inductances together. Such a unit is ordinarily known as an impedance bond. Where the .return current is of medium or low value the track rails themselves may be relied upon as of sufificient capacity to carry the return current. In those systems, however, Where traffic is heavy additional multiple conductors are necessary. Also, under certain conditions, especially where clearances are small and where the hazard is great, as for instance in subways, "tunnels and overbridges, it is desirable to provide additional protection against derailment. This may be accomplished by running an additional pair of rails between the ordinary track rails, these additional rails being spaced closely to the usual rails so that the flanges of the car wheels may pass between the two adjacent rails, and are for con.-

venience called guard rails.

In accordance with the present invention it is proposed not only to provide such guard rails, but it is also proposed to use these guard rails to aid in the carrying of the return current. It would, however, not be safe 'to bond these guard rails together at various points, because'lf this were done loops of extremely low resistance would result, which would act as asecondaries of a transformer where the track circuit itself constitutes the primary. Such a short circuited guard rail loop of low resistance would not only interfere with the proper operation of the track. circuit with which it is inductively connected but would cause alternating current toflow in such loop circuit which alternating current might 'be conducted. to the rear of a. passing train so that it could be'picked up by a following'trainand in so doing signify clear traffic" conditions on the fol- 56 lowing train even though there were a train directly ahead. It is therefore proposed, in accordance with the present invention, to place an insulating joint in each guard rail at various points along the track, these points being preferably spaced a number of blocks apart, and the insulated ends of these guard rails being connected together through a high inductance, the midpoint of which is connected to the return conductor. Such an impedance would greatly restrict the flow of alternating current in the loop circuit 10 but would not materially interfere with the flow of propulsion current.

Other objects, purposes and characteristic features of the present invention will in part be more specifically described hereinafter and will in part 15 be obvious from the accompanying drawing showing one embodiment of the present invention.

Referring to the drawing the main track rails I of the railway system embodying the present invention are preferably divided into blocks by in- 20 sulating joints 2, of which the blocks A, B, C, D and. E and the adjacent ends of two other blocks only have been illustrated. Since all of these blocks are the same only the devices of one block will be described, like devices of other blocksbeing 25 identified by like reference characters having distinctive exponents.

Referring to the block A, this block preferably has a signal S at the entrance end thereof, the normal direction of traffic being from left to right 30 as indicated by the arrow in block C. At the exit end of this block A is provided the usual transformer TR which is connected across the track rails through the medium of a series resistance T and in turn is connected in series with the track relay T connected across the rails at the entrance end of the block. This transformer 'IR resistance '1 track rails l and track relay 'T are connected in series and comprise the usual elements of a normally closed track circuit. 40

At the junction of two successive blocks, in those systems where propulsion current, whether direct or alternating of low frequency, is employed, is provided an impedance bond designated BO for the bond located at the exit end 45 of the block A. Each of these impedance bonds comprises two inductances of low resistance each connected across the rails on opposite sides of the insulating joints 2, with their midpoints connected by a conductor of low resistance. These 50 impedance bonds permit the free flow of direct current, or alternating current of low frequency, from block to block, this because if the current is equally divided between the track rails the current flowing in these inductances magnetically neutralize each other, so that current may fluctuate without difficulty. The alternating track circuit current of higher frequency, however, will not flow through the inductance of the bond by reason of the high impedance that the bond offers to the flow of alternating current from one rail to the other of a block, because the impedances of the two halves of a bond are cumulative. The net result is that very little alternating current flows through the bond.

The various signals S S S S S and S are controlled by the various track relays T T T T T and T in any suitable well known manner so as to cause the first signal to the rear of a. train to indicate stop, to cause the second signal to the rear of a train to indicate caution and to cause the third signal to the rear of a train to indicate proceed, all as well understood by those skilled in the art of railway signaling.

The alternating current flowing in the track circuit may inductively transmit to suitable carcarried apparatus the conditions of trafiic in advance as reflected by the current coded or noncoded in the track circuit. This has been conventionally illustrated by a car-carried control relay CR energized by coded current received from a suitable amplifier Amp, the in-put side of which is connected to inductoriums or receivers RS? and RS It will be observed that the relay CR when so energized extinguishes lamp R and energizes lamp G, signifying clear track conditions, and when deenergized energizes lamp R signifying that the train is occupying a caution or danger block.

Although the coded cab signaling system constituting a portion of applicants system may be of the three or more indication type, for convenience a two indication cab signaling system has been illustrated.

Referring to the drawing, each block is provided with an approach relay AR, which is energized only if the associated block at the exit end of which it is located is occupied as reflected by contact 20 and the next block in advance is unoccupied, as reflected by contact 2| in the control circuit. From this control circuit and the manner in which the contact 22 of relay AR controls the track circuit of the associated block, it is apparent that non-coded alternating track circuit current is applied to the block when the next block in advance is occupied, resulting in energization of the red lamp R in the cab, and that if the next block in advance is unoccupied coded current derived through coder commutator 23 is applied to the associated block resulting in energization of the green lamp G. Also that no current will be received by the amplifier Amp when the block in which the train is moving is occupied by another train in'advance thereof.

Although the manner of energizing the track transformer TR has only been illustrated for the blocks A, B and C, the remaining block of the system in practice have their track transformer energized in the same manner. I

It is well known that track circuits are subject to ballast leakage; that is, current flows from rail to rail through the ground or along the surfaces of the ties. This leakage is governed by the distance from rail to rail and-by the conductivity of the intervening space. It is obvious that where guard rails are employed, set between the rails and joined at their ends to the midpoints of impedance bonds the effective leakage distance is very much shortened, in fact is only two times the space between a running rail and the adjacent guard rail. When, however, the guard rails are terminated at impedance bonds in accordance with my invention the efiective leakage path is increased by the impedance value of the bond and operating conditions are much improved.

In addition to the usual and well-known apparatus just described it is contemplated to provide guard rails I0 properly bonded together end to end in the usual way and provided with insulating joints spaced at much greater distances than are the insulating joints of the regular track rail, these insulating joints having been illustrated by gaps l2 in these guard rails Ill.

The ends of the guard rails for each section end are connected together through an inductance I, the midpoint of which is connected to the return conductor l5, connected at the power house to a generator Gen, the other terminal of which is connected to the trolley wire I6, adapted to be engaged by the trolley pole H. In like manner, the midpoint of the bonds adjacent each of the insulating joints l2 are likewise connected to the return conductor l5. As shown, the bonds B0 and B0 only have been shown connected to the return conductor I5. The bonds B0 B0 B0 and B0 are not so connected because a certain small amount of track circuit current might, as under broken rail conditions, flow through the bond and through the return conductor [5 to produce an unsafe condition. If, however, these bonds B0 are connected to the return conductor IE only at points spaced substantially five blocks apart the stray current so flowing would be so small that its efiect is negligible and may be disregarded.

In the system, accordingto the present invention, even though a small amount of current may be induced in the loop circuit through the guard rails 10 and the inductances I and I in series, the current so induced will be of such small value that its effect on the receiving apparatus of a train in the rear of another train will be negligible and may be disregarded. Applicant has thus provided a system in which the propulsion return current may not only flow over the two usual rails in multiple, but may also flow in multiple over guard rails adjacent thereto, without in any way interfering with the proper and safe functioning of an alternating current track circuit provided for each block by the running rails; and furthermore although the propulsion current circuits created by the guard rails are of extremely low resistance, these circuits are of suificient impedance due to the inductances of h the bonds I that the alternating currents of track circuit frequency induced in the closed circuits thereof are so small as not to interfere with the proper operation of the track circuits itself, and are so small as not to be detected by the receiving apparatus on a train in the rear of another train. Also, if desired, there may be more guard rail sections than blocks or even a plurality of such sections per block.

Having thus shown and described one specific embodiment of the present invention it is desired to be understood that the particular system illustrated has been shown to exemplify the present invention rather than to show its scope and that certain changes, modifications and additions may be made as required by local conditions all without departing from the spirit or scope of the present invention or the idea of means underlying the same.

What I claim as new is:

1. In an electric propulsion railway system, the combination with a railway track having its track rails divided into blocks by insulating joints, an alternating current track circuit for each block each track circuit including the usual alternating current source and a track relay in series, impedance bonds connecting adjacent blocks, guard rails adjacent said track rails to guard against derailment and to afford a return path for propulsion current, and impedance bonds for connecting said guard rails together.

2. In an electric propulsion railway system, the combination with a railway track having its track rails divided into blocks by insulating joints, an alternating current track circuit for, each block each track circuit including the usual alternating current source and a track relay in series, impedance bonds connecting adjacent blocks, guard rails adjacent said track rails divided into sections by insulating joints and to guard against derailment and to afford a return path for propulsion current, and impedance bonds for connecting said sections.

3. In an electric direct current propulsion railway system, the combination with track rails divided into blocks by insulated joints, an alternating current track circuit including a source of alternating current and a track relay in series for each block, an impedance bond for each block junction including a reactance for each adjacent block end having their middle points connected together, guard rails extending the full length of several blocks adjacent the track rails for guarding a train against derailment, a return conductor for conducting the propulsion current back to the source of propulsion current supply, and inductances each connecting the ends of said guard rails and having their middle points connected to said return conductor.

4. In an electric current propulsion railway system, the combination with track rails divided into blocks by insulated joints, a track circuit including a source of current and a track relay in series for each block, an impedance bond for each block junction including a reactance for each adjacent block end having their middle points connected together, guard rails extending the full length of several blocks adjacent the track rails for guarding a train against derailment, a return conductor for conducting the propulsion current back to the source of propulsion current supply, and inductances each connecting the ends of said guard rails and having their middle points connected to said return conductor.

5. In an electric direct current propulsion railway system, the combination with track rails divided into blocks by insulated joints, an alternating current track circuit including a source of alternating current and a track relay in series for each block, an impedance bond for each block junction including a reactance for each adjacent block end having their middle points connected together, guard rails adjacent the track rails and electrically divided into sections by air gaps, a

returnconductor for conducting the propulsion current back to the source of propulsion current supply, and impedance bonds connecting together the guard rails at each end of each section and having their mid-points connected to said return conductor.

6. In an electric direct current propulsion railway system, the combination with track rails divided into blocks by insulated joints, an alternating current track circuit including a source of alternating current and a track relay in series for each block, an impedance bond for each block junction including a reactance for each adjacent block end having their middle points connected together, guard rails adjacent the track rails and electrically divided into sections by air gaps, a return conductor for conducting the propulsion current back to the source of propulsion current supply, inductive means joining the said guard rails at the end of each section to permit alternating current to flow in multiple in said guard rails of a section but to greatly restrict the flow of alternating current in a loop circuit comprising such guard rails in series with said inductive means. i

'7. In an electric direct current propulsion rail- Way system, the combination with track rails divided into blocks by insulated joints, an alternating current track circuit including a source of alternating current and a track relay in series for each block, an impedance bond for each block junction including a reactance for each adjacent block end having their middle points connected together, guard rails adjacent the track rails and electrically divided into sections by air gaps, a return conductor for conducting the propulsion current back to the source of propulsion current supply, inductive means joining the said guard rails at the end of each section to permit alternating current to flow in multiple in said guard rails of a section but to greatly restrict the flow of alternating current in a loop circuit including said guard rails in series.

8. In a train cab signaling system, the combination with track rails divided into blocks by insulating joints, impedance bonds connecting the rails of adjacent blocks to permit the flow of propulsion current, a track circuit for each block having current flowing therein in accordance with traffic conditions in advance, train-carried means including cab signals controlled in accordance with the flow of current in the track rails ahead of such train, guard rails adjacent the said track rails to guard against derailment and divided into sections by insulated joints, a propulsion current return conductor, and impedance bonds connecting said guard rails to said return conductor so as to impose a high impedance to alternating current flowing in a loop circuit including the guard rails of a section but to impose a low impedance to the flow of alternating current flowing in the guard rails in multiple and to said return conductor.

WADE H. REICHARD. 

